Watt-hour meter



Jan. 21, 1941. T. D. BARNES v WATT HOUR METER Filed June 9, 1957INVENTOR w. m m m Patented Jan. 21, 1941 UNITED STATES PATENT oFi-"icEWATT-HOUR METER Pennsylvania Application June 9, 1937, SerialNo..147,215

3 Claims.

The present invention relates to an improved form of clamping device andis described with specific reference to a means for clamping the baseand cover of a watt-hour meter of the detachable type. It should beobvious from the following description that the invention is of widerapplication.

In meters of the so-called detachable type, the meter movement ismounted upon a comparatively flat circular base plate and is enclosed bya glass cover, the rim of which rests upon such plate. The cover andplate are suitably clamped in interlocking relation to exclude foreignmatter, as by providing inter-engaging means on the base plate and on aflange secured to the rim of the cover to be engaged by relativerotation between the cover and base plate. For example, the flange onthe cover may be provided with spaced inwardly projecting portions toconstitute cam surfaces, and segmental projections on the base plate maybe fofced under such portions to a desired extent to clamp the base andcover together. A set screw or similar device cooperating with the baseplate and flange may then be used to prevent further relative rotation.

The position of the set screw must be predetermined, that is, the baseplate and flange must always be rotatable to a predetermined relativeposition for cooperation with the screw. This is difficult becausemanufacturing discrepancies incident to large quantity production resultin suflicient variation in the dimensions of the plate and flange tocause the clamping action to be too tight or too loose when the partsare in position.

to receive the set screw.

The type of construction described above is shown in some detail inBradshaw et a1. Patent 1,969,499, issued August 7, 1934.

It is an object of the present invention to provide a clamp structureincluding a cam surface with means for slightly relieving the cam actionas the clamped position is approached so that a more uniform clampingaction may be obtained in spite of manufacturing discrepancies toprevent freezing of the clamped parts but at the same time insuring adesired clamping action.

Other objects will be apparent from the following description and theaccompanying drawing, in which: Figure 1 is a view in rear elevation ofa watthour meter of the so-called detachable type,

Fig. 2 is a view with parts broken away in elevation of the structure inFig. 1, and

Fig. 3 is a view in section taken on the line III-III of Fig. 1.

With more specific reference to the drawing, the meter casing comprisesa base plate 2 having a centrally raised portion and four contact blades4 suitably secured to and insulated from the base plate by insulation 6and cotter pins 8 which cooperate with the blade terminal N) (Fig. 3) onthe opposite side of the plate to retain the blade in position. i

The periphery of the base plate 2 is provided with three outwardlyprojecting segmental portions 12 (Fig. 1) which constitute part of theinterlocking structure of the invention.

Referring to Figs. 2 and 3, showing the meter casing in invertedposition for the purpose of clearness, the plate 2 is provided with aglass cover M of cup shape having an outwardly extending peripheral rimIt. A metallic rim I8 is secured to the flange I6 in any suitablemanner, as for example, as disclosed in the aforesaid patent to Bradshawet al. No. 1,969,499.

The rim l8 has an inwardly extending flange embracing the cover flangel6 and the rim extends vertically to a point above the normal plane ofthe periphery of plate 2.

As shown in Fig. 1, at three equally spaced I points the verticallyextending portion of rim I8 is bent inwardly and, as shown in Fig. 2,the inwardly bent portion is not parallel to the plane of the base butis inclined thereto so that the undersurface of it will constitute a camsurface.

In assembling the structure described, a gasket 22 (Fig. 3) is placedupon the face of the cup edge and the base 2 is laid upon it in suchposition that the projecting segments l2 are to the right of theinwardly extending portions 29 of the rim I8. The base 2 is then rotatedin the direction of the arrow in Fig. 1, bringing the segments l2 underthe cam surfaces formed by projections 20. Under ideal conditions with agiven turning force applied to the base 2 such rotation will properlyclamp the base to the cover [4 at such position that a set screw 24extending through an inturned lip 26 on the rim I8 will register withan. aperture in the base plate 2 and a nut 28 in a recess in the coverface for securing the parts in clamped relation. As a practical matter,however, particularly in a case involving quantity production ofthousands of meters per month, exact dimensions of the parts describedcannot be adhered to and there is certain to be sufilcient inaccuraciesto render it difficult to rotate the base plate 2 to its clampedposition and at the same time have the lip 26 in proper position for thescrew to extend through the aperture in the base plate 2.

In order to correct this difficulty, it is proposed that the rim [8 beprovided with slots 30 extending beneath the cam portions 20. The slotsin effect weaken the vertical portion of the rim IE3 at different pointsto afford more latitude in rotating the plate segments 20 beneath thecam surfaces. It will be noted that in this case the slots extend fromthe open end of the cam to a point short of the lower end of the cam andare substantially parallel with the plane of the plate 2. As a result,the increasing clamping action imposed by the cam, as the plate 2 isrotated into position, is progressively relieved as the final or clampedposition is approached. However, the slot terminates short of the finalposition, at which the set screw 24 may be applied, so that the reliefin pressure is abruptly terminated to prevent the base from being pulledthrough the cam beyond such final position. Quite obviously, the extentof the relief in pressure depends upon the distance between the slot andthe face of the cam and such distance may be so chosen that with a givenforce for rotating the base 2 with respect to the cover, the base may bebrought into its proper clamping position to receive the set screw 24 inan expeditious manner. Also the action may be varied as desired bylengthening the slot or changing its position with respect to the camsurface.

Quite obviously, the invention is capable of modification within thespirit thereof and it is intended that it be limited only by the scopeof the appended claims.

I claim as my invention:

1. In combination with a receptacle of cup shape and a cover therefor, arim secured to the receptacle having an upstanding flange with inwardlyprojecting portions on the periphery thereof, means carried by saidcover proportioned to extend under said projecting portions to beclamped thereby against the edge of the receptacle, said projectingportions being so proportioned that upon relative rotation of thereceptacle and cover said means may enter under one end of theprojecting portion and be pressed against the receptacle edge with anincrasing force as it is moved toward the other end of the projectingportion, means comprising a slot in said rim extending along saidprojecting portion for relaxing said force as said other end isapproached and means for securing the rim and cover in a final positionagainst further relative movement.

2. In combination with a receptacle of cup shape and a cover therefor, arim secured to the receptacle having an upstanding flange with inwardlyprojecting portions on the periphery thereof, means carried by saidcover proportioned to extend under said projecting portions to beclamped thereby against the edge of the receptacle, said projectingportions being so proportioned that upon relative rotation of thereceptacle and cover said means may enter under one end of theprojecting portion and be pressed against the receptacle edge with anincreasing force as it is moved toward the other end of the projectingportion, means comprising a slot in said rim extending along saidprojecting portion substantially parallel to the plane of said cover forrelaxing said force as said other end is approached and means forsecuring the rim and cover in a final position against further relativemovement.

3. In a detachable enclosure assembly, a base member, a cover member,said members cooperating to define an enclosure, and means fordetachably connecting said members including a substantially circularrim carried by said cover member and projecting outwardly from its pointof attachment to said cover member and beyond the end thereof towardsaid base, a camming structure including circumferentially spaced camelements carried by said rim and extending circumferentially thereof,each cam being positioned beyond the point of attachment of said rim tosaid cover member, a slot in said rim positioned adjacent each cam andextending circumferen tially of the rim between each cam and said pointof attachment, each of said slots extending from a point adjacent theforward end but terminating short of the rear end of each cam thusproviding a partially detached weakened rim portion, and a lip elementcarried by said base member cooperating with said cam to clamp the coverto said base in camming relationsln'p, said weakened rim portion beingadapted to yield during the initial camming movement.

THOMAS D. BARNES.

